Understanding Polarizers

Care, Feeding & Proper Use
There are few more important things that a naturephotographer can do to improve his or her photography than becoming familiarwith the use of the polarizing filter.
What can a polarizing filter do for you? Among other thingsit can darken the sky, remove reflections from water, and make foliage appearless shiny. Colour saturation is also significantly enhanced. It is the onlyfilter for use with colour film that can do all of this.
Lone Crane — Yucatan, 2002
Photographed with a Pentax 645NII andPentax (67) 200mm f/4 lens on Provia 100F — Polarizer
As seen above the use of a polarizing has been effective in removing reflectionsand glare from the surface of the water, and also in increasing the saturationof the colours beneath the water. The remarkable colour is cased by run-offfrom the surrounding mangrove swamp near the estuary in Celestún,Yucatan, Mexico. (See below for moreontaming reflections).

Polarization and Wide Angle Lenses
There are two issues to keep in mind when using apolarizing filter and a wide angle lens. The first is that the angle ofpolarization varies continuously with the angle from the sun. With a lens widerthan about 28mm (in 35mm film terms) the sky will be unevenly polarized.Some pundits therefore suggest not to use a polarizer with ultra-wide lenses.Nonsense. If you like the effect, go ahead and use it.
Tumbleweed Dunes, 2000
Photographed with a Rollei 6008 and 40mmf/3.5 Schneider Super-Angulon on Fuji Provia 100F
This photograph taken inMonumentValley shows this effect — to a fault. I used a polarizing filter with awide angle lens; equivalent to about a 24mm lens in 35mm terms. The part ofthe sky that‘s at 90 degrees to the sun is heavily darkened while the area tothe right, closer to the position of the sun, is much less polarized. Nevertheless,I like the effect.
Polarization is most effective at 90 degrees to the sun. This means that thesubject that you are shooting will display maximum  polarization at rightangles to the sun‘s position. At 180 degrees, in other words with the sun rightbehind you, polarization is almost non-existent.
An old trick for visualizing the maximum angle is to turn your index fingerinto a gun (like when you were a child), with your thumb pointing upward.Make as if to shoot the sun with your finger and your thumb will point towardwhere polarization is at its most extreme. Remember though that this isn‘t justat one angle. Rotate your wrist through 180 degrees (if you can), because theentire circle around the sun is equally polarized.
The second issue with polarizers and very wide-angle lensesis the thickness of the filter. By their nature polarizers are thick filtersbecause they have a double ring — the first of which mounts the filter to thelens and the second which is the rotating polarizing element itself. If the lensis wider than about 24mm, when used at small apertures the edge of the ring cancause vignetting at the corners of the frame.
The solution is to buy a "thin" polarizer. Theseare made by B+W and Heliopan, among others. Their downside is thatthey are even more expensive.
While discussing brands — even though polarizers are themost expensive filter that you‘re likely to buy, it‘s definitely worthpurchasing a top brand, like one of the above, rather than a cheapy. Store-brandpolarizing filters can often "separate" after several years of use inharsh conditions. Try not to skimp in this area if you don‘t absolutely have to.

Circular Vs. Linear Polarizers
There are two types of polarizing filters available —linear or circular. Linear polarizers are more effective and less expensive thancircular ones. But circular polarizers are needed with just about any camerathat has a through-the-lens metering system, or autofocus.
The reason for this is that both of these systems usesemi-silvered mirrors to siphon off some of the light coming though the lens. Ifthat light is linearly polarized it renders either the metering or the autofocusineffective. This means that you‘re going to have to buy circular polarizersunless you‘re shooting with a pre-1970‘s camera, or a view camera.

Sunglasses
The easiest way to preview the effects of polarization isto wear polarized sunglasses. Just remember when looking at a scene to tilt yourhead from side to side to change the angle of polarization. If you feel thatthis makes you look like a bird searching for food, simply take the sunglassesoff and hold  them in front of you as you rotate them. If you wear prescriptionglasses you can order them polarized the next time that you renew.
The problem with wearing polarized sunglasses is that whenyou then put a polarizing filter on your camera and look through the viewfinderthe two polarizers can cancel each other out and completely darken theviewfinder. What I do is to use sports strings on my glasses and temporarilyadjust the diopter on the viewfinder so that I don‘t need to wear my glasses.This is a good reason to always purchase a camera that has an adjustableviewfinder diopter. Inserting and removing interchangeable screw-in diopters inthe field is simply too slow and inconvenient.


I find that a polarizer is most effective for me in taming reflections,either in water or foliage. (See as well the example at the top of the page).The two frames above were scanned together tominimize difference in post processing. The first frame was taken without apolarizer, the second one with. Look at the rock and moss around the cascadingwater and also at the water in the foreground. The use of a polarizer hassaturated the colours and made the image much more effective.
Iceberg Canyon, Lake Powell UT — April, 2001
Photographed with a Mamiya 7 and 65mmf/4 lens on Provia 100F with custom Mamiya Polarizing Filter

Stitched Panoramics
As nice as it would be to use a polarizer when producingstitched panoramics this is a bad idea, as each panel will be unevenly polarizedand the skies will never be made to match up.

Using a Polarizer with a Rangefinder Camera
Since it‘s necessary to visually "tune" a polarizingfilter, some people believe that it‘s not possible to use one with a rangefindertype camera. This isn‘t  so. Some manufacturers have created ingenioussolutions (such as for theMamiya7), but there‘s a simpler way. If you have a polarizer that has markingsaround the rim simply hold the filter in front of you while pointing at thesubject and note the angle of the mark. If it‘s at say 11 o‘clock at maximumpolarization, then put the filter on the camera and turn it so that the markis again at 11 o‘clock when it‘s on the lens. Heliopan polarizers areto be preferred for this reason because they have continuous numerical marksaround the periphery of the filter which makes doing this quite simple.

Controlling Costs
Polarizing filters are expensive, and circular polarizerseven more so. But you really must have one to fit every lens in your arsenal.Doing so can therefore be pricey.
There are a couple of ways of dealing with this. One is tobuy a single polarizer of the largest size that you need and then to buystep-down rings to fit it to your smaller lenses. This can be a finicky task inthe field when you‘re working in a hurry, or in cold or wet conditions. It mayalso be difficult to find step-down rings that can take from, say, a 95mm filterdown to a 52mm size. And, if the smaller lens is also a wide angle lens, thenvignetting will likely occur.
For these reasons the best solution that I have found is touse a comprehensive filter system like that from Lee, my favourite. Thisallows you to only have to buy one set of filters of all types (especiallygraduated / split neutral density filters) and then with an adaptor for eachfilter size needed use the same filters on all your lenses.
In late 2001 Lee brought out a large circularpolarizer that attaches to the front of their "Foundation Kit".If you use this then this one polarizing filter will be the only one that youever need to buy.
I have found though that unless you reduce the number offilter slots in the Foundation Kit to one this combination will vignettewith any lens wider than about 28mm. Such is life.

Exposure Control
One final thought, and that‘s with regard to exposurecontrol. If your camera has a TTL metering system then compensation for thefilter will  be automatic. On a manually metered camera you‘ll need to openup about 1.5 stops. I say "about", because the exact amount willdepend on the degree of polarization.
For this reason I tend to bracket critical shots taken witha polarizer, even if the camera has a TTL metering system. In this circumstance,as in many others, the right exposure isn‘t necessarily the best exposure.

On Reflection
A polarizing filter is the most productive accessory that a photographercan have in his kit, second only to a decent tripod and head. Don‘t leave homewithout one.